Abnormal sperm morphology: What does it mean?

Sperm morphology — the size and shape of sperm — is checked as part of a standard semen analysis for male infertility. The results of a sperm morphology exam indicate the percentage of sperm that appear normal when semen is viewed under a microscope.

Normal sperm have an oval head with a long tail. Abnormal sperm have head or tail defects — such as a large or misshapen head or a crooked or double tail. These defects may affect the ability of the sperm to reach and penetrate an egg.

However, having a large percentage of misshapen sperm isn't uncommon — and it won't necessarily keep a man from getting his partner pregnant. In fact, a sperm sample isn't considered out of the normal range unless most of the sperm are abnormally shaped. If pregnancy does occur, having abnormal sperm morphology doesn't increase the risk of having a child with birth defects.

In addition to sperm shape, a sperm analysis also checks the sperm's ability to move (motility) and the number of sperm present (sperm count). Motility problems and a low sperm count commonly occur along with abnormal sperm morphology, and can also affect male fertility.

If a semen analysis shows abnormal sperm morphology or other irregularities, a wait-and-see approach is generally tried first. Another semen analysis is usually done after four to six weeks to see whether sperm quality has improved on its own. If there are still large numbers of abnormal sperm or a low sperm count, tests may be necessary to look for an underlying problem.

In some cases, sperm problems are due to a permanent condition — such as a testicle abnormality present at birth — and can't be treated. In other cases, sperm quality improves when an underlying condition gets better. Some common causes of abnormal sperm that are temporary or may be reversed with treatment include:

• Enlargement of veins within the scrotum (varicocele)
• High fever
• Use of certain illegal drugs
• Infection

Even with abnormal sperm morphology, motility problems or a low sperm count, pregnancy may still be possible. However, pregnancy doesn't always occur right away. For some couples, it can take a year or more. If you and your partner aren't able to conceive through sexual intercourse, assisted reproductive technology such as in vitro fertilization may be an option.